Battery Load Testing

Want to know how to load test a car battery without a fancy tester? Your car has everything you need right onboard to do the test without the use of a voltmeter or load tester. I have created this guide which will go over an easy step by step instruction process that will allow you to test your own battery while saving you a considerable amount of money.

Here are the main reasons the unit will fail:

  • Battery is more than three years old
  • The alternator is not charging or over charging the electrical system
  • There is a electrical (parasitic) draw on the system
Now if you are sure the battery is the problem then this is the test for you but, if you are not sure and you are on the page because the engine wont crank over then you will need to do some checking first. Learn more

To get started please watch the video below then follow down the guide to see what additional information has been added to this subject.

Now then, let's get started.

To begin you must take note if the charging system warning light, is on while driving? This warning might be a symbol or a volt gauge needle that is low toward the minus sign. If so then the fault maybe the alternator not outputting enough voltage and must be checked first. Learn more

If the warning light is not on or gauge shows it the system it charging or the charging system checks out okay using a voltmeter let's continue.

A battery can fail in one of two ways, the first way is very quickly in others word you go out to your car and without warning it will be just dead. When this happens there isn't much you can do but wait for a tow truck or someone you know to give you a jump start using jumper cables. In this case a jump may not even help because the battery is so far gone it just dumps (pulls in) all the voltage supplied to it.

The second way the battery can go bad is a slow decline of voltage and amperage which gives you little signs along the way such so slow engine cranking. Once you notice this it's up to you to be preventive and change the unit out before total failure occurs. The best way to confirm this is with the following test:

Step 1

When working with a battery wear protective eyewear and gloves, stand clear of the battery while the engine is cranked over. Open the hood to locate the battery and check it's condition, you are looking for leakage and bulging which indicating warped internal plates that can short circuit and also corrosion which can eat the positive and native cable away which will cause additional problems. These are all signs the unit is having a problem.

Now, turn the headlights on and leave them on for about 20 minutes.

Step 2

After waiting the allotted amount of time and the headlights still on, try cranking the engine over while observing the headlight bulb brightness. The bulbs should only dim slightly when using the starter, if they dim way down and go out or you notice the engine is cranked over slowly followed by a machine gun style of clicking noise, the battery can not supply the voltage needed to operate and must be replaced. Learn more

If the unit was good it should be able to withstand this load test.

The electrical cables that supply power and ground can inhibit electrical flow, look for bulges near the top of the cable ends near the terminals. These bulges indicate corrosion expansion caused by the chemical reaction between the acid and copper wire inside the cable and should be replaced.

A non deep cycle battery must have a rest or downtime to allow the plates inside time to cool. A battery subjected to constant charge and complete discharge will fail prematurely unless it is a deep cycle type unit. All batteries are a hazardous material and must be disposed of at a local parts store or recycle center.

If you have any question about the information or testing you have just read about please visit out forum where thousands of questions have already been answered. Learn more


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